Additive
manufacturing for all
Gemma Church investigates the applications and issues of moving additive manufacturing into the mainstream
However, the various additive manufacturing (AM) processes available are still in their infancy and face challenges to enable the mass production of parts that can pass performance guarantees required by industry. Simulation provides key insights into design
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and build decisions to push the different AM processes out of the research arena and into mainstream industrial production, but process reliability and repeatability must be ensured to make this a reality, as Alan Prior, vice president SIMULIA Worldwide Center of Simulation Excellence at Dassault Systèmes, said: ‘Physics- based simulation offers a way virtually to engineer the process to minimise unwanted effects like stress and distortion in printed parts, so that successful prints can be achieved without time- consuming and costly test iteration in the real world. Tis will exponentially accelerate progress towards widespread adoption.’ One of the core challenges for AM process
simulation is the multi-scale nature of the problem. Alonso Peralta, principal investigator at technology house Honeywell, explained: ‘Te
24 SCIENTIFIC COMPUTING WORLD
dditive manufacturing, commonly known as 3D printing, is widely used for the manufacture of plastic prototypes and consumer products.
difficulty that arises with numerical simulations in additive manufacturing is the large temporal and spatial scales that are transcended in the problem.’ Tere are many different AM processes that
vary in their method of layer manufacturing. Powder bed fusion methods use either a laser or electron beam to melt and fuse material powder together. Dr Peralta said: ‘In this process, we are trying to melt powder particles that are less than 100 microns in diameter, and we have to build parts that are less than a metre in size. Furthermore, we must melt the powder where the interaction time of the laser and the powder is in the order of a few microseconds and it takes up to a few days to make a complete part.’ Tis increases the complexity of the
simulations, as Mustafa Megahed, manager of CFD and Multiphysics Centre of Excellence at the ESI Group, explained: ‘Models also have to deal with multiple physical aspects, such as heat transfer and phase changes, as well as the evolution of the material properties and residual stresses throughout the build time. Te modelling task is, therefore, a multi-scale, multi-physics endeavour calling for a complex interaction of multiple algorithms.’ Another limitation is the lack of well-
characterised material data to understand detailed phase transformation effects and fatigue responses. Experimental data is aiding development in this area, alongside molecular- level material simulation, according to Prior: ‘We can create atomistic models of material concepts to study these effects, and through our continued development efforts we will link this molecular scale simulation with part-level simulation.’ Computational consulting company AltaSim
Technologies is focused on the laser powder bed fusion of metallic powders to produce metallic components for aerospace. Tis comprises two research areas: shape optimisation, which aims to produce a component at a minimum weight while meeting target mechanical properties, and AM process physics, with studies ranging from fundamental evaluations of the laser beam- particle interaction to estimates of residual stress/distortion in AM components. Simulating AM process physics is a challenge,
says Jeffrey Crompton, principal at AltaSim Technologies: ‘Of these, shape optimisation is perhaps more readily handled with existing capability whereas analysis of AM process technology is complicated because of the wide spread of deposition schemes available and the complexity of the interdependent phenomena that need to be included in any analysis.’ Te range of issues associated with AM
process physics is extensive, from determining the best powder size distribution to minimising
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